IIT-Madras professor explains why dosas are crispy on outside & soft on inside
The dosa, a staple food in South Indian cuisine, has been a topic of fascination for many food enthusiasts. The perfect dosa is a delicate balance of crispiness on the outside and softness on the inside. But have you ever wondered what makes a dosa achieve this perfect balance? According to Prof Mahesh Panchagnula from IIT-Madras, the secret lies in the way the dosa batter interacts with the hot tawa, and it’s all linked to a phenomenon known as the Leidenfrost Effect.
For those who may not be familiar, the Leidenfrost Effect is a phenomenon where a liquid, in this case, water, comes into contact with a surface that is significantly hotter than its boiling point. When this happens, the water droplets do not immediately evaporate, but instead, they form a thin layer of vapor between the liquid and the hot surface. This vapor layer creates a cushioning effect, allowing the liquid to glide and float on top of the surface.
Prof Panchagnula explains that the practice of sprinkling water on a hot tawa before pouring the dosa batter is a classic example of the Leidenfrost Effect in action. When the tawa is not hot enough, the water evaporates slowly, and the dosa batter sticks to the surface. However, when the tawa is heated to the right temperature, the water droplets form a thin vapor layer, allowing the dosa batter to glide and float on top. This prevents the dosa from sticking to the surface and creates a crispy exterior.
But how does this phenomenon contribute to the softness on the inside? According to Prof Panchagnula, the Leidenfrost Effect plays a crucial role in creating a temperature gradient within the dosa. As the dosa batter cooks on the hot tawa, the outer layer is subjected to high temperatures, causing it to crisp up. However, the inner layer remains at a lower temperature, retaining its moisture and softness. This temperature gradient is made possible by the Leidenfrost Effect, which allows the dosa to cook evenly and retain its softness on the inside.
The Leidenfrost Effect was first identified in Germany in the 18th century by Johann Leidenfrost, a German physician and theologian. He observed that when a liquid comes into contact with a surface that is significantly hotter than its boiling point, it forms a thin layer of vapor between the liquid and the surface. This phenomenon has since been studied extensively in various fields, including physics, engineering, and materials science.
In the context of dosa making, the Leidenfrost Effect is a critical factor in achieving the perfect balance of crispiness and softness. By sprinkling water on the hot tawa before pouring the dosa batter, the cook creates a thin vapor layer that allows the dosa to glide and float on top. This prevents the dosa from sticking to the surface and creates a crispy exterior, while the inner layer remains soft and moist.
In addition to the Leidenfrost Effect, there are several other factors that contribute to the perfect dosa. The type of rice and lentils used, the proportion of ingredients, and the fermentation process all play a crucial role in determining the texture and flavor of the dosa. However, according to Prof Panchagnula, the Leidenfrost Effect is a critical factor that sets the stage for the perfect dosa.
In conclusion, the next time you enjoy a crispy dosa with a soft interior, remember the science behind it. The Leidenfrost Effect, identified in Germany in the 18th century, plays a crucial role in creating the perfect balance of crispiness and softness. By sprinkling water on the hot tawa before pouring the dosa batter, the cook creates a thin vapor layer that allows the dosa to glide and float on top, preventing it from sticking to the surface and creating a crispy exterior.
Source: https://x.com/iitmadras/status/1993901259925909929
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